1. Field of the Invention
The present invention relates to an improvement in an insulated type switchgear device, and more specifically, to an improvement in a vacuum type switchgear with multifunctions in which a pair of arc electrodes are designed to be separable through rotation of a movable conductor around a predetermined main axis.
2. Related Art
A commonly used transformer substation includes such components as transformers, circuit breakers and disconnecting switches, and an electric power from the transformers is supplied via the circuit breakers and disconnecting switches to loads such as motors. When performing maintenance and inspection of the loads, these circuit breakers as well as the disconnecting switches which are provided separately from these circuit breakers are opened, and further, by means of a grounding device remanent electric charges and inductive currents at a power source side are sinked into a ground so as to ensure safety of maintenance persons.
In these switchgear devices, for example, in a vacuum circuit breaker, circuit making and breaking operations are performed by engaging and disengaging a pair of arc electrodes which are disposed in a vacuum tube.
In general, a vacuum circuit breaker having a structure in which a movable conductor is moved with respect to a stationary conductor in a vertical direction by means of an operating mechanism disposed outside the vacuum tube so as to engage and disengage the pair of arc electrodes, each provided at one end of the respective movable and stationary conductors, is frequently employed.
Further, a vacuum circuit breaker as disclosed, for example, in JP-A-55-143727(1980), in which a movable arc electrode is designed to engage and disengage with a stationary arc electrode through rotation of the movable arc electrode around a predetermined main axis, is also used.
Generally, in a circuit breaker, when an arc stays at a portion between the arc electrodes during a circuit breaking operation, the surface temperature of the arc electrodes increases due to thermal input from the arcing to thereby cause melting of the metal of the arc electrodes. In such an instance, consumption of the arc electrodes is significant as well as surplus vapour metal particles existing between arc electrodes extremely reduces its circuit breaking performance. Therefore, in vacuum circuit breakers and in particular those for interrupting a large current, a variety of measures are applied for the structure of the arc electrodes.
For example, with spiral electrodes in which spiral ditches are provided for the arc electrodes, an arc is provided with a driving force in a rotating direction by a current flowing through the arc electrodes and is always moved between the arc electrodes to thereby suppress the melting of metal on the surface of the arc electrodes.
Further, with coil shaped electrodes provided at the back faces of the arc electrodes, magnetic flux in the axial direction of the arc electrodes is generated to thereby diffuse the arc uniformly between the arc electrodes and to reduce current density of the arc.
However, conventional insulated type switchgear devices contain the following problems. Namely, in the conventional insulated type switchgear devices as disclosed, for example, in JP-A-3-273804(1991), circuit breakers, disconnecting switches and grounding switches therefor are separately manufactured and installed, therefore, the size of the device is increased. Further, with the circuit breaker making use of a rotating movement operation in which the engagement and disengagement with the stationary arc electrode is performed through rotation of the movable arc electrode around a predetermined axis, the pair of arc electrodes are placed in an offset position when performing a circuit breaking operation. Therefore, a region which allows an arc ignition (in other words the effective area of the arc electrodes) decreases, and thereby the circuit breaking performance thereof is likely reduced.